Can't ssh with long NIS usernames

While I can ssh with NIS usernames 8 characters or less, I'm unable to with longer usernames. Until I set max_logname=21 I couldn't even su to the accounts. So, now I can su to them, but I can't ssh as them. The errors are:
- sshd[258240]: Failed password for testuser1234 from 192.168.1.2 port 45371 ssh2
- ssh: failed login attempt for testuser1234 from zeus

If I could find a clear/concise howto on how to use AD, then I
would gladly use it. In fact, the NIS server I'm using is via
the AD server. I've tried using kerberos on AIX but couldn't
get it to work and NIS is braindead simple...as long as the
usernames are 8 characters or less apparently.